We talk with leading educators in the field of asphalt technology in an effort to tune in to academia on important industry issues.
Y. Richard Kim is a Distinguished University Professor and Alumni Association Distinguished Graduate Professor in the Department of Civil, Construction and Environmental Engineering at North Carolina State University.
What drew you to civil engineering, and in particular, transportation?
I chose civil engineering in my undergraduate program because of the large-scales of civil infrastructure systems that civil engineers work on. Before I came to Texas A&M University for my master’s degree in the summer of 1983, I had not studied asphalt engineering. While looking for an assistantship and thesis research topic, I consulted Drs. Little and Lytton and became fascinated by their research. Once I discovered the beauty of asphalt materials, I knew what my career path would be.
What are some of the best ways to evaluate chip seals and fog seals?
Evaluation of pavement preservation treatments, such as chip seals and fog seals, has relied on mostly empirical methods. However, more advanced techniques and methodologies can be adopted in evaluation of the preservation treatments; these can improve the performance and life of these treatments. The North Carolina Department of Transportation has sponsored a series of research projects for NC State University to develop and use these methods to improve preservation treatments’ specification, design and construction. These methods are currently used in the NCHRP Project 09-50 to develop performance-related specifications for binders used in pavement preservation treatments.
Are there new technologies or strategies to help pavement designers prevent cracking?
Polymer-modified asphalts have shown better resistance to cracking. Various mechanisms contribute to the performance enhancement that has been seen from different polymer-modified asphalts, including their ability to recover deformation, the ability to deform more without cracking, the ability to dissipate the energy into tiny micro-cracks and the ability to heal these micro-cracks. Cracking is not just a material-related problem; pavement structural design is also important in preventing cracks. Perpetual pavements based on fatigue endurance limits are a means to direct the cracks to places where maintenance and rehabilitation are less costly (e.g., pavement surface instead of the bottom of the pavement).
Are there new developments in testing warm mix asphalt?
Warm mix asphalt is becoming a major material type for the U.S. highway network. It is not only environmentally friendly, but also saves money and makes paving construction easier if used properly. As more types of warm mix asphalts are introduced into the paving community, it is important to develop a nationally accepted performance testing program. The major challenge in testing warm mix asphalt is how to replicate the conditions in the field in the laboratory testing program. There is enough evidence in some early field trials that laboratory test methods traditionally used for hot-mix asphalt do not predict the performance of warm mix asphalt in the field.
Where should today’s engineering students focus their research in the asphalt field?
Asphalt engineering is a complex discipline due to the nature of the material and the loading and environmental conditions to which the material and the structure are subjected. It is becoming even more interdisciplinary with the introduction of new materials, such as warm mix asphalt, recycled asphalt pavement, recycled asphalt shingles and bio-asphalt, to name a few. Consequently, today’s asphalt engineers should have solid understanding in physical and chemical aspects of the materials. Otherwise, it will be impossible to develop specifications and design methodologies for ever-changing material compositions. Students should learn the basics of asphalt engineering first. The practical aspects of asphalt engineering can be learned when students obtain real jobs. However, the opposite does not work in most cases.
